A slit-like opening in a container is commonly formed by the tearing of a sidewall of the container with the tear propagating along a weakened line. The weakened line is formed in the sidewall during manufacture of the container. The weakened line typically comprises a line of perforations (or small cuts) in the sidewall or, alternatively, an elongated area of reduced thickness of the material forming the sidewall. The tear commonly is initiated by a pull-tab that is easily grasped with fingers and pulled to create a shear force in the sidewall of the container along the weakened line. FIGS. 1 and 2 respectively illustrate a conventional weakened line 20 that is formed in a sidewall 22 of a flexible food storage bag 24, and the resultant opening 26 formed in the bag when the sidewall is torn along the weakened line.
Containers made of plastic material, such as a plastic film food storage bag, commonly exhibit the characteristic that the plastic material is very difficult to puncture but, once a tear has been initiated in the material, the tear propagates very easily. When a tear is made to form a slit-like opening in the food storage bag, more often than not the tear propagates beyond the weakened line thereby enlarging the opening beyond its intended dimension. Consequently, the product contained in the bag can spill out during the opening of the bag depending upon the extent that the sidewall is torn beyond the weakened line defining the intended opening. Furthermore, if the opening is designed to be reclosable, the extended tearing of the sidewall usually impairs the reclosable feature of the bag.
A need therefore exists for the provision of a means for limiting the propagation of the tear from beyond the weakened line thereby insuring that the opening formed does not exceed the intended opening for which the container is specifically designed.